call back (Noun) — The recall of an employee after a layoff.
call back (Noun) — A return call.
call back (Noun) — A request by the manufacturer of a defective product to return the product (as for replacement or repair).
call back (Verb) — Cause to be returned. ex. "The manufacturer tried to call back the spoilt yoghurt"
call back (Verb) — Have and bring to mind a memory of something; bring back knowledge from memory.
call back (Verb) — Return or repeat a telephone call. ex. "I am busy right now--can you call back in an hour?" ex. "She left a message but the contractor never called back"
call back (Verb) — Summon to return. ex. "The company called back many of the workers it had laid off during the recession"